Temperature controlled purge valve with washer/o-ring seal stack

ABSTRACT

In a valve having a body with a sealed working fluid chamber, a bore and a valved fluid chamber, the valved fluid chamber having an inlet and outlet and a seat between the inlet and the outlet, a piston for extending through the bore from the working fluid chamber to the valved fluid chamber, a spring for biasing the piston away from the seat and a working fluid for receipt in the working fluid chamber. Applicant provides an improvement comprising a seal stack assembly for entrainment, under compression, upon the piston and in the piston chamber between a working fluid chamber end wall and a first end of the piston, wherein the first end of the piston is located in the working fluid chamber and a second end in the valved fluid chamber.

This is a utility application, which claims priority to and the benefitof U.S. Application No. 62/063,985, filed Oct. 15, 2014, andincorporates herein by reference U.S. patent application Ser. No.14/065,857, filed Oct. 29, 2013; U.S. patent application Ser. No.11/275,135, filed Dec. 13, 2005; and U.S. Pat. No. 6,892,747.

FIELD OF THE INVENTION

Temperature controlled valve for water systems, including water well andwater softener freeze protection, as well as other system water flowcontrol.

BACKGROUND OF THE INVENTION

Water well and water softener systems use pressurized water in pipes orother elements that are sometimes exposed to cold temperatures. Freezeprotection in the past has typically utilized wrapping exposed elementswith electrical heat tape or insulation or a combination of bothmethods. While these solutions are often satisfactory for mostconditions, there exists a need for a non-electrical, non-passive systemthat engages pressurized elements of water supply assemblies foractively preventing freeze-up by temperature, with the use of thepressurized systems water, to purge the chilled water and subsequently,and as a direct result of purging, replace with warmer water.

This action prevents the devices from freezing. There is also the needfor flow control in water systems wherein water cooler than ambient isneeded downstream of a water supply.

SUMMARY OF THE INVENTION

A water carrying pressure bearing system comprising a source of waterpressure is provided. Water bearing lines or water bearing containersare sometimes exposed to external air temperature fluctuations orambient water conditions. Downstream of the source of water, freezeprotection is provided. Protected system elements are in fluidcommunication with a water bearing line and the source of waterpressure. In the water bearing line, there is a purge valve with aworking fluid which may undergo a phase change, the working fluidtypically having a freezing point above 32° F., the valve in fluidcommunication with the water bearing line. In one embodiment, the valveis biased to a normally closed position at temperatures above thefreezing point of the working fluid. The valve opens as the workingfluid contracts and freezes. The working fluid may be, in oneembodiment, selected from fluids with freezing points being in the rangeof about 32° F. to about 50° F. or preferably about 34° F. to 45° F. Thevalve may have an outlet engaged therewith to carry away water receivedtherein when the valve opens responsive to cooling air on an air sensingportion. The valve may be moderated by a water temperature sensing side.The protected elements, in three embodiments, comprise a water softenercontroller valve, a water trough, and a pressure switch for any numberof uses or systems.

In a first embodiment of several, Applicant provides an active,non-electrical, air and water temperature responsive purge valvedownstream of a well water pump and upstream of a pressure sensingswitch in a water distribution system, which may include a water welland pressurized water tank. In a second embodiment, Applicant provides asimilar valve on a pressure line downstream of a water softener. Fluidflow directly from the well pump, tank or other pressure source may beabout 56° F. to 65° F., no matter the ambient temperatures. Purge valvesin both embodiments are typically located in outside air, where they maybe subject to contact with both the water in the system and the outsideair. The valve contains a chamber having a material selected frommaterials which freeze between the temperatures of about 32° F. and 50°F., most preferably about 41.5° F. In doing so, the freezing workingmaterial contracts to allow a spring biased valve to open on a waterpressure line, which valve then dumps or bypasses fluid from a high side(which may be well water pressure tank pressure) to a low side bypass,which may be ambient pressure. In doing so, pressure relief in thesystem at a temperature above the freezing point of water, generatesfluid flow from the well and/or pressure tank or other source, therebypreventing freeze-up. In a preferred embodiment of Applicant's valve,there is a range of cross-sectional area ratios between water contactingelements of the valve and air contacting elements of the valve.

In a valve having a body with a sealed working fluid chamber, a bore anda valved fluid chamber having an inlet and outlet and a seat between theinlet and the outlet, a piston for extending through the bore from theworking fluid chamber to the valved fluid chamber. A spring is providedfor biasing the piston and a working fluid is provided for receipt inthe working fluid chamber. The working fluid is, in one embodiment, analkane. An improvement comprising a seal stack assembly is provided forengaging the piston in the piston chamber between a working fluidchamber end wall and a first end of the piston. The first end of thepiston is located in the working fluid chamber. A second end of thepiston is in the valved fluid chamber. The seal stack assembly comprisesat least one elastomeric element and one hard element, both elementscoupled to the piston such that the spring urges the second end of thepiston in the direction of the first end. The hard element may be awasher with at least one slot in a side wall thereof.

A valve is provided having a body with a sealed working fluid chamber, abore and a valved fluid chamber. The valved fluid chamber has an inletand outlet and a seat between the inlet and the outlet. A piston isprovided for extending through the bore from the working fluid chamberto the valved fluid chamber. A spring is provided for biasing the pistonaway from the seat. A working fluid is provided for receipt in theworking fluid chamber. A seal stack assembly is engaged, undercompression, upon the piston and in the working fluid chamber between aworking fluid chamber end wall and a first end of the piston. The firstend of the piston is typically located in the working fluid chamber anda second end in the valved fluid chamber proximate the seat such thattemperature changes cause the piston to move responsive to expansion andcontraction of the working fluid between a seated and an unseatedposition, the unseated position for the passage of a fluid past theseat.

A thermally actuated valve is provided comprising: a housing havingwalls defining an inlet adapted to receive water under pressure, anoutlet, a first chamber fluidly connecting the inlet to the outlet, asecond chamber having a near end and a removed end. Walls define a boreseparating the first chamber from the second, longitudinal chamber. Aresilient seat defines a seat plane, the seat for engaging the housing,the seat adjacent the inlet of the first chamber of the housing. Apiston has a first end that includes a nose and a second end and alongitudinal axis. The piston is partially disposed in the firstchamber, partially and slidably disposed in the bore, and partiallydisposed in the second chamber. The piston's longitudinal axis isaligned substantially perpendicular to the seat plane. A spring engagesthe piston, so as to bias the piston towards the removed end of thesecond chamber. A seal stack assembly fluid seals between the piston andwalls of the second longitudinal chamber and is sandwiched undercompression between the spring and walls of the second chamber toprevent fluid transfer between the first chamber and the second chamber.A working material is sealed in the second chamber to move the pistonresponsive to temperature changes between a seated position and anunseated position.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are schematic illustrations of Applicant's novel valve asused in a water well system and a water softener system.

FIG. 1A is a schematic illustration of details of the relationshipbetween a mechanical purge valve and a pressure switch.

FIGS. 1B and 1C are illustrations of an electrical embodiment ofApplicant's purge valve for use in close proximity to a pressure switch.

FIGS. 2A and 2B illustrate cross-sectional areas of a first, watercontacting portion and a second, air contacting portion, respectively,of Applicant's novel valve.

FIGS. 3 and 4 illustrate side cross-sectional views of an exampleembodiment of Applicant's novel valve in a closed and open position,respectively.

FIGS. 3A and 3B are cross-sectional views (valve opened and valveclosed) of an alternate preferred embodiment of the purge valve in whicha stack assembly is used in the fluid compartment, rather than O-rings33 a/33 b in the piston rod channel or bore between the fluid chamber ofthe working fluid and the water side.

FIG. 3C is an exploded view of a stack assembly for use in the alternatepreferred embodiment of the purge valve as set forth herein.

FIG. 3D is an exploded perspective view of an alternate preferredembodiment of a stack assembly.

FIG. 3E is a perspective view of an alternate preferred embodiment ofthe stack assembly on a piston for use in a purge valve.

FIG. 4A is a cross-sectional detail view of the multi O-ring seal ofFIG. 4 showing the lubricant used therewith.

FIG. 5 is a side elevation cutaway of the purge valve (open).

FIGS. 6 and 6A illustrate the use of a remote purge port for pipedownstream of the purge valve.

FIGS. 7A, 7B, and 7C provide cross-sectional cutaway views of anotherexample embodiment of Applicant's present mechanical purge valve inthree conditions: FIG. 7A, warming a water source responsive to coolambient temperatures; FIG. 7B, cooling a water source responsive to warmambient temperatures; and FIG. 7C, valve closed condition, the valve notaffecting the flow of water through the system.

FIG. 8 is a partially schematic view of a cattle trough water flowsystem that is adapted to use Applicant's novel valve in any of theembodiments illustrated.

FIG. 9 is a cross-sectional view of a valve showing a method ofcalibrating Applicant's mechanical valve so it opens and closes at theproper temperatures.

FIGS. 10A, 10B, and 10C illustrate an alternate preferred embodiment ofApplicant's stack assembly, which may be referred to as a “integral”one-piece stack assembly.

FIGS. 11A and 11B illustrate an alternate preferred embodiment of thestack assembly

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates Applicant's purge valve 10 as part of a water wellassembly 100 and FIG. 2 illustrates Applicant's valve as part of a watersoftener assembly 200. FIGS. 3, 4, and 4A illustrate details of anexample of purge valve 10 having a first body portion 30 and a secondbody portion 32, with a sealing area or piston bore 33 therebetween, anda valve seat 34. A temperature/pressure responsive piston 38 opens abypass port 36, and controls the flow of water through the bypass port36 when the temperature drops below a set point, such as in the range ofabout 32° F. to 50° F., which set point is typically about 10° above thefreezing point of water. Piston 38 is responsive to a change in volume(at phase change) of a working fluid 40, which working fluid fills afluid chamber 42 in the first body portion 30 of the valve. When workingfluid 40 (which is typically not water based) in chamber 42 reaches apoint, it will contract as it loses heat and changes phase from a liquidto a solid at the freezing point of the fluid, and will cause piston 38,biased open by a spring 44, to retract from valve seat 34. This allowswater well and/or pressure tank pressurized water to flow through thebypass port 36 and out an outlet or purge port 37. Further details ofApplicant's novel valve will be set forth after an explanation of itsuse in the system.

Turning to FIG. 1, it is seen that system 100 may include a water well112, such as a domestic or commercial (municipal) water well, which mayhave a pump 114 (mechanical or electrical), such as submerged pump orany other pump suitably located to draw water from below the groundlevel of the well. A water supply line 115 provides the water underpressure through a pressure switch 120, to a pressurized water tank 116.Demand from users downstream of pressure tank 116 will allow water toflow out through line 118 to provide their needs. Pressure switch 120 istypically provided somewhere in the system (typically at, or upstream ofpressure tank 116), responsive to pressure changes in tank 116, suchthat below a low set pressure, pump 114 will be activated and providewater to tank 116, and above a high set pressure, will shut off.

FIG. 1 illustrates Applicant's well water well assembly 100 providingvarious downstream water uses of the water from the water well assembly100. These uses may include use in a commercial or residential structure216, in a cooling tower, such as those known in the art for cooling thehot side of air conditioners 218, and a livestock animal trough 220, asset forth in more detail hereinbelow.

Pressure switch 120 may be of the diaphragm type and when exposed totemperatures near or below 32° F., especially when windy, can freeze upfaster than any other part of the well assembly. They then becomenon-responsive to pressure changes in the system. When this occurs, apressure drop in the pressure tank will not initiate a signal to startthe pump, and the system has failed mechanically and is subject tofurther freezing and potential damage to equipment.

Use of Applicant's purge valve 10 in the system, typically at orupstream of tank 116 and typically close to the pressure switch, willhelp ensure that under even severe weather conditions, the purge valve,acting independently of the pressure switch, will help preventfreeze-up.

Applicant's water well assembly may have pump 114 which may be amechanical water pump, such as a mechanical or a sucker rod pump or anelectrical pump (or any other suitable pump). It may have a storagetank, which may be a pressurized storage tank, gravity feed storage tankor any suitable water storage tank for receiving water pumped from adomestic, commercial or agricultural water well. Typically, one or morewater flow control devices are a part of the water well assembly tocontrol the water pumped as it is used by downstream elements of thewater well assembly.

FIG. 1A illustrates a schematic detail view showing the manner in whichApplicant's purge valve 10 may be used with a fluid pressure sourcepressurizing a pressure switch.

In FIG. 1A, a pressure switch 120 as known in the art, may includediaphragm 120 a responsive to water pressure in pressure switch mountpipe 121, may engage one arm of electrical contacts 120 b to close oropen the contacts and energize/de-energize a remote pump responsive towater pressure in a pressure source and responsive in some embodimentsto pressure in a pressure tank as set forth herein. A tee or horizontalmember 122 may extend perpendicular to the typically vertical pressureswitch mount pipe 121. In any case, Applicant's purge valve 10 istypically located below the pressure switch 120 and in a manner that itmay open and gravity drain, for example, through purge port 37, fluidfrom contact with the diaphragm. This will prevent freeze-up fromdamaging the diaphragm. It will also initiate a pump “on” condition bydraining some water from tank 116. The pump will re-pressurize thesystem with, typically warmer water which, in turn, will help shut thepurge valve 10. It will also initiate an “on” condition, by drainingwater from the pressure tank, which forces the pressure switch to turnthe water well pump on, and refill the tank and piping with warmerwater.

FIG. 1A illustrates that, in one embodiment, purge valve 10 is usuallywithin a minimum distance (measured by fluid pathway) of about ¼ inch toabout 12 inches from the diaphragm of the pressure switch. This willhelp protect and prevent freeze-up of the pressure switch.

FIGS. 1B and 1C illustrate an alternate preferred embodiment ofApplicant's system. Wherein the other systems set forth herein use amechanical purge valve 10, it is noted that, in conjunction with apressure switch, a solenoid purge valve 126 powered by a power circuit127 may be used in close proximity to the pressure switch so that it maydrain from a gravity fed outlet 128, water or other fluid at a pressuresource 121. That is to say, instead of a mechanical valve 10, a solenoidvalve 126 may operate with a circuit which includes power 123 (battery,DC, AC, solar or any suitable source) and a thermostat switch 130.Thermostat switch 130 will typically be set for the same approximaterange as the mechanical purge valve, that is closing at least severaldegrees above freezing and opening solenoid valve 126 to allow fluid todrain before freeze-up at the pressure switch. As seen in FIG. 1C,thermostat switch 130 (or a sensor therefor) may be placed adjacent oron elements, metallic or non-metallic, downstream of solenoid valve 126.At position 2 or 3 as seen in FIG. 1C, when warmer water from a well,for example, flows through an open the solenoid valve, thermostat switch130 may open causing the solenoid valve to close, thus re-pressurizingthe pressure switch with, typically, warmer water. Position 1, FIG. 1C,locates switch 130 in air, while positions 2 and 3 are both water andair temperature exposures.

Further details of purge valve 10 may be appreciated with reference toFIG. 3. First portion 30 may be referred to as “air exposed” portion andcontains an external surface, typically cylindrical and constructed ofbrass or other suitable metal, which also may be referred to as the airtemperature sensing portion of purge valve 10. A second portion 32 hasan interior that may be subject to the presence of stationary water (orempty) when the valve is closed and which carries water in an open or“protect” mode and is subject to the temperature bias of the purgedwater as it is discharged. In an alternate preferred embodiment, thebody defined by elements 30/32/33 may be made of plastic, such asDelrin®.

In a situation where the air temperature cools suddenly, for example,with the passage of a sudden cold front, first portion 30 will cool morequickly, subject as it is to exposure with the air, especially movingair, and second portion 32 will lag, subject to the water or proximityto system water and the contact with the water within (valve open) bodyportion 32 or proximate (valve closed) to body portion 32. Water isknown to moderate temperature changes (it has a much higher specificheat than the material, typically brass or other suitable metal, ofwhich the valve body is made). Warm water within portion 32 willtypically provide warmth to portion 32, which by conduction will providesome heat to portion 30 as it drops below the set point. Thus, portion32 will have the effect of moderating air caused temperature changes ofportion 30, so that especially with sudden changes of air temperature,sufficient heat may flow from portion 32 to 30 to moderate and preventtoo quick a freeze-up of working fluid 40 (and thus a draining of waterfrom the system).

FIGS. 3 and 4 illustrate purge valve 10 in a closed and open positionirrespectively. Working fluid chamber 42 is sealed at a first end byremovable threaded cap 20. Cap 20 may use an O-ring 22 on a shoulderthereof to tightly seal working fluid 40 in fluid chamber 42. Typically,the working fluid will be sealed into the chamber when in its liquidphase. The set point is calibrated by advancing the plug until the nose38 a of piston 38 is sealed in seat 34 which, in one embodiment, is anO-ring (see also FIG. 9). Spring 44 biases valve piston to the openposition (see FIG. 4). However, fluid pressure of working fluid 40 influid chamber 42 holds the valve in the seated or closed position attemperatures above the set point. At these temperatures, the workingfluid will expand slightly (compared to set point) to maintain a goodseat, especially in an elastomeric seat, such as valve seat 34. However,as the air temperature cools through the set point, the working fluidwill begin to undergo phase change and contract, thereby temperatureproportionally opening valve as in FIG. 4. This will allow water to passinto the valve and out the port, utilizing the ambient pressure PW (seeFIG. 3), which pressure is generated by the pressure tank and/or pump.

FIGS. 4 and 4A illustrate the use of an anti-seize lubricant 33 c, whichhas a freezing point less than water. These lubricants may be used tofill in, around, and between the O-rings that separate the chambercontaining the working fluid and the chamber through which purged fluid,typically water, will pass out of when the purge valve is opened.Tolerances between the piston and the body may be plus or minus 0.001inch. It is seen the lubricant tends to be held in between the spacesthat separate adjacent O-rings and the piston walls where they contactthe body.

When the purge valve opens, water will be drawn through the channels ofsecond body portion 32 and out the drain port to dump onto the ground,to recycle in the well (as illustrated in FIG. 1) or for other suitabledisposal. This water will typically be warmer than air temperature andwill warm the surrounding material of portion 32. Heat by conductionwill flow to portion 30.

Working fluid 40, in certain embodiments, will undergo a phase change atabout 41.5° F. (5.5° C.), which is approximately 10 degrees above theFahrenheit freezing point for pure water. One such material is an alkaneknown as Tetradecane (C₁₄H₃₀), which undergoes a volumetric contractionof about 20% at the freezing/melting point (range 39-43° F.) as measuredfrom a liquid phase to a solid phase. Preferably, working fluid 40 wouldundergo a phase change from liquid to solid contracting at the phasechange, which freezing (melting) point is in the range of about 6° toabout 18° F. above the freezing point of water in one embodiment.

In some embodiments, cross-sectional area a of second body portion 32 istypically larger than cross-sectional area p of first body portion 30(see FIGS. 2A and 2B). The metallic or plastic elements defining thebody of the valve may, in particular embodiments, be brass (specificheat of approximately 0.1). The range of the larger area, that is, thecross-sectional area of second body portion 32 which contacts the watermay be in the range of 1.2 to 4 times the cross-sectioned area of theair sensitive first body portion 30.

Turning to FIGS. 2, 6, and 6A, a water softener system 200 isillustrated, which has a water softener pressurized on a pressurizedwater source 210, which may be water well or water pressure tank or citywater. FIGS. 6 and 6A illustrate Applicant's use of purge valve 10 on awater softener assembly 200 downstream of a water softener tank 214.Water from water softener tank 214 is pressurized, and purge valve 10 istypically exposed to ambient conditions. Pipes 212 downstream of tank214, and other elements of the system may be exposed to cold air, as ina garage, shed or outside of a building. As such, they may benefit fromuse of Applicant's purge valve 10, which may be “teed” or otherwiseinstalled into a water pressure bearing outlet, such as soft wateroutlet line 211, that is subject to cold temperatures. In the samefashion as set forth with the water well assembly 100, cold airtemperatures will generate purging of the pressurized lines, which flowwill maintain the circuit in a flow condition, for a period of time, toprevent freeze-up. The use of Applicant's valve is an alternative toleaving faucets on inside the house (so as to keep water flowing insystem), which can waste water if ambient temperatures are abovefreezing and may let pipes freeze if the faucet discharge is less thanwhat is needed for very cold temperatures. The use of Applicant's purgevalve 10 in either assembly will reduce such water wastage, whilepreventing the assembly from freezing.

FIG. 5 illustrates the use of a vacuum break 46 in a threaded drainfitting 47, which will help prevent siphoning when the removed end of adrain tube 48 has water in it. Vacuum break 46 will also provide a wateroutlet, should any portions of drain line 48 freeze up. Drain tubes 48are typically placed so that the removed end thereof is adjacent to adrain or goes back into the well.

FIG. 5 also illustrates the use of a sleeve or jacket 50, which istypically shaped with an open end 52 and a body 54, and a closed end 55,that will slip on and snugly engage the exterior portion 30 to act as ashield and insulation from the possibilities of wind, sleet, snow, iceand/or their accumulation, from affecting the air temperature sensitivesecond body portion 30 of purge valve 10. Such an insulation jacket 50may be made from 1/10 inch pliable plastic or suitable materialtypically with a thermal conductivity less than metal, or may be an airgap.

In FIGS. 3, 4, and 4A, it is seen that working fluid 40 is sealed influid chamber 42 by cap 20 at one end. Sealing area or bore 33 may havemultiple O-rings 33 a/33 b in grooves, which O-rings are urged againstthe outer wall of piston 38. One system of O-rings or other elasticmaterial that has proved to be an effective seal to maintain the workingfluid sealed in and to resist the pressure generated by expansion of theworking fluid may be found in U.S. patent application Ser. No.11/275,135, which is incorporated herein by reference.

Purge valve 10 may be placed on a water well close to the pressureswitch, approximately ¼″ to 12″ from the pressure switch in certainembodiments. The purge valve may be placed on or near the water softenercontrol box or downstream of the water softener. In general, Applicant'snovel purge valve may be used anywhere on any system where there is aneed to prevent freeze-up of pipes.

Turning to FIGS. 3, 4, and 5, basically, the following summarizes someof the structure and functionality of the valve:

First body portion 30:

Cylindrical, typically metallic, defines an inner chamber

External surface exposed to ambient air; internal containing chamber 42which contains the working fluid and removed end 38 b of piston 38

Sealing plug or cap 20 for sealing working fluid and pressurecalibration (typically screw)

Spring 44 to bias “open”

Optional jacket or sleeve see FIG. 5) for exterior of metallic cylinder

Second body portion 32:

May take any external or internal configuration within an internal watercavity/chamber 31

Chamber 31 bordered longitudinally with sealing area (see below), andbypass port 36, and also containing a vertical trending purge port 37

Metallic heat flow path between (among) T₁ of water in chamber 31, T₂ incylinder (working fluid 40) first body portion 30, and T₃ (air) onexterior surface of second body portion 32 (see FIG. 4)

Sealing area or bore 33, located longitudinally between body portions 30and 32 (see FIG. 4) for locating piston 38

Multiple seals adapted to withstand pressure in system

Seals on both sides of a leak vent 39 (prevent leakage) typicallylubricant filled (prevents moisture and debris accumulation)

O-rings 33 a on working fluid side prevent leakage of the working fluid

O-rings 33 b on water side prevents leakage of water into a leak vent 39

Use of an anti-seize/lubricant compound 33 c (FIG. 4A), on and aroundthe O-rings is preferably food/drug grade

FIG. 3 shows purge valve 10 in the closed position. However, purge valve10 in the closed position may have nose 38 a of the piston past valveseat 34, that is to the right of the position of the nose with respectto the valve seat as seen in FIG. 3—such that in a closed position, theO-ring or other element defining valve seat 34 is on the cylindricalbody portion of the piston. Regarding the valve seat, it may be anO-ring or other suitable elastomeric material. Regarding the O-rings 33a/33 b or other sealing members of bore 33, they are made of anelastomeric material that does not dissolve or react with the workingfluid, but provides an effective fluid seal against the body of thepiston. Anti-seize/lubricant compound 33 c, such as a food gradesilicon-based composition, may be used on and around the piston/O-ringinterface. FIG. 4A illustrates the use of a low temperature (below thefreezing point of water), anti-seize/lubricant compound 33 c around andbetween the multiple O-rings 33 a/33 b that the piston moves over.

Turning to FIGS. 5, 6, and 6A, an optional purge port tube 56 may beprovided to remotely locate a removed end 56 a from a near end 56 b.Near end 56 b is engaged with a fluid tight couple to the purge valveinlet. When purge valve 10 is in a closed position, the water softener,well water or other pressure source is in a normal (non-freezingenvironmental) condition, with the purge valve and all elements thereof“invisible” to the system. However, when the air temperature gets coldoutside and first body portion 30 communicates a temperature drop bycooling the working fluid to freezing, the valve will then open anddrain fluids out through bypass port 36 and purge port 37 and/orexternal drain tube 48. However, because of the use of purge port tube56 placed in an annulus of pipe DS downstream of valve 10 and engagingthe inlet of the second body portion 32, some of the purged fluid isbeing drawn from the remote removed end 56 a and, therefore, flows allthe way through the annulus between the tube 56 and the inner walls ofthe DS pipe purging it of cooling water and generating flow, with warmerfluid coming in and preventing freeze-up. Note that removed end 56 a istypically located past where the pipe annulus enters the interiorenvironment, whether that be just below ground or just inside a wall(see FIG. 6 or ghosted lines, FIG. 6A). In either case, the effect ofusing purge port tube 56 with removed end 56 a located in a warmernon-ambient, non-outside air temperature environment is to maintain flowthrough all of the pipe annulus, even portions downstream of the purgeport during cold weather. Arrows at A in FIG. 6A show flow of water whenthe valve gets cold and opens (piston and seat omitted).

FIGS. 7A, 7B, and 7C illustrate an alternate embodiment 10′ ofApplicant's valve. Structurally, the difference in the previousembodiment (see, for example, FIGS. 3 and 4) lies in the structure ofpiston 138. In the alternate embodiment 10′ of the valve, piston 138 isseen to have a nose 138 a, which has an annular recess 141. The annularrecess is dimensioned such that in a “valve warm” condition (FIG. 7B),wherein expansion of the working fluid 40 in chamber 42 has, throughexpansion responsive to the warm air/ambient water temperatures, pushedthe tip of nose 138 a past O-ring or valve seat 34, so that annularrecess 141 is adjacent to the seat. This is the condition seen in FIG.7B and it may be seen that cool fluid (relative to air temperature) maypass through the space created by the annular recess and out purge port37 to provide water from the well or storage, which will typically becooler, to elements downstream of drain port 37. In this manner,Applicant's alternate embodiment 10′ acts to provide cool fluid, thatis, cooler than air/ambient water temperature, to elements downstream ofthe valve. Embodiment 10′ will also prevent freeze-up (see FIG. 7A) inthe manner of valve 10.

Applicant has found that, in the summer, livestock, while thirsty and inneed of water, are reluctant to drink water from a trough when the waterin the trough is too warm. What Applicant provides therefor in analternate embodiment 10′ of the valve is the ability of the valve pistonto “overshoot” the seat and place the annular recess 141 adjacent theseat and allow cooler water from tank 304 to flow into trough 306. Waterin the tank 304 is typically cooler in the summer than the surroundingair temperature and the water temperature in the trough, and warmer inthe winter than the surrounding air temperature and temperature of thetrough, containing as it is, a large warm water received from theground.

FIG. 8 illustrates a use of Applicant's alternate embodiment 10′ in alivestock watering system 300. Livestock watering systems are used toprovide water for livestock in pastures and feedlots and may comprise awater pump 302 engaging a water well 303. Water pump 302 may be awindmill using a mechanical pump as well known in the art of windmillwater pumping. Pump 302 may also be electrical. As illustrated in FIG.8, pump 302 may pump water from well 303 into an elevated tank or otherwater tank 304 (pressurized or gravity feed) for selectively supplyingwater to a nearby trough 306. A conduit 308 is typically provided withApplicant's valve, in either embodiment, but in the embodimentillustrated 10′ at the removed end of conduit 308 and typically beneathwater level WL of trough 306. In some cases, a parallel water feedsystem 310 may be provided to bring water to trough 306 responsive towater level or float valve 312. Such float valve 312 controlled waterlevel systems are well known in the art. Applicant's system provideswater to trough 306 separate from and not controlled by the float valvesystem, if one is present.

As is seen in FIG. 8, first body portion 30 and, in fact, the entirepurge valve 10 or 10′ may be submerged below typical water levels in thetrough. However, the valve might be in air positioned so it drains waterinto the trough when opened. As seen in FIGS. 7A-7C, Applicant's valve10′ is adapted to provide water that is cooler or warmer than apreselected water temperature range. Typically, the water in the troughhas a greater surface area exposed to cold or warm air temperatures thanthe larger volume of water in tank 304 and thus will reach a cooler orwarmer temperature sooner than the storage tank in the same airtemperature, humidity, and wind conditions. Thus, the valve opencondition of FIG. 7A, which typically occurs at temperatures up to about18° F. above the freezing point of water, will open and allow relativelywarmer water from the tank 304 to enter the trough to prevent icebuildup when the air temperature is cool. When the air gets warm, it canwarm the trough water and a condition as seen in FIG. 7B can result.This will allow cooler water to flow into the trough.

FIG. 9 illustrates threadably removable cap 20 adapted to engage theremoved end of second body portion 32, so as to seal fluid chamber 42.Cap 20 may have a recessed tool receiving section 20 a on an exteriorsurface thereof, and an annular recess 23 on the near end thereof forholding an O-ring 22 (see also FIG. 3).

FIG. 9 also illustrates a method of calibrating the piston so that itseats and unseats at the proper temperatures. In this method, the valvehousing is held vertically in a fixed position and the working fluid,liquid at room temperature, is used to fill fluid chamber 42. At thispoint, the spring will have the piston fully retracted (see FIG. 4). Inthis method, the valve housing is typically held vertically in a fixedposition and the working, liquid at room temperature, is used to fillthe fluid chamber 42. At this point, the spring will have the pistonfully retracted from the seat (see FIG. 4, for example). The spring isnot under compression, the cap is off, and the fluid chamber is fullyfilled. The cap (which may be self-tapping) is then threaded in withrotor tool 317 until the O-ring 22 contacts the inner walls of the fluidchamber. Further rotation of the cap compresses the working fluid, thenmoves nose 38 until it is against a dial indicator gauge/limit switch315 and/or limit switch. The dial indicator gauge/limit switch actuatesto turn off the rotary tool 317 when the nose, at room temperature, hasmoved to the preselected position past the seat as indicated in FIG. 9.Further warming will simply move the nose slightly further down, as seenin FIG. 9, but the dial indicator gauge and/or limit switch 315 hasproperly positioned the nose with respect to the seat, such that thevalve will unseat when the first set temperature, typically the freezingpoint or freezing range of the working material, is reached, opening thevalve as seen in FIG. 4 or 7A.

The combination of a pressure switch with Applicant's mechanical orelectrical purge valve in close proximity thereto, may be used in anysuitable environment where the pressure switch may be exposed to ambientfreezing conditions. Exemplary of these environments are the following:water wells, reverse osmosis systems, ice machines, water level controls(depth gauges and large tanks), aerobic septic systems, lawn sprinklersystems, fire sprinkler systems, geothermal AC systems, cooling tower ACsystems, and gray water distribution systems. While the 0 to about 12inches is measured typically from the diaphragm surface along the waterpath to the inlet of valve 10 or solenoid 126, other distances may besuitable, including preferably between about 2 to about 8 inches.

There are many instances where a valve that opens in response to achange in temperature allowing water flow is beneficial. One suchinstance is the protection of water pipes from freezing. Anotherinstance is the freeze prevention of livestock drinking troughs that aresubject to freezing conditions. In some cases, it is useful to use afluid with a phase change melting point at the desired valve actuationtemperature. Alkane paraffins may be commonly used, as they exhibit alarge change in volume at their respective melting points and there aremany to choose from.

One useful alkane that may be used in the construction of automaticwater valves for freeze prevention is N-tetradecane with a melting pointof 42° F. (4° C.), that is, above the freezing point of water. Thisfreezing point may be lowered as desired by the addition of a suitable“antifreeze” such as N-dodecane.

In one embodiment, an alkane working fluid is contained in a chamberclosed by a moveable piston rod at one end. As the alkane freezes, itcontracts, allowing the piston to be urged by spring pressure to slideand open a water valve seat that is constructed at the other end of thepiston rod. Upon warming, the alkane melts and expands sliding thepiston rod against spring pressure to close the water valve seat.

For this device to be constructed, a slideable seal or stack assemblyallowing movement of the piston rod but effectively separating thealkane working fluid from the water may be useful. Also a means ofsupporting the piston rod may be useful.

An object of the following embodiment is to provide a seal in the formof a stack assembly for the piston rod in a temperature responsivevalve. With a stack assembly, sealing area or bore 33 typically nolonger uses “O” rings 33 a/33 b (see FIG. 4), the sealing function beingprovided by the stack assembly located in the first body portion 30.

FIGS. 3A, 3B, and 3C illustrate an O-ring/washer seal stack assembly(hereinafter sometimes “stack assembly”) 400 (FIG. C) and 400′ (FIGS. Aand B). It typically comprises multiple alternating washers and O-ringsfor engagement upon a piston as set forth hereinbelow for providing,among other things, the O-rings for sealing against the passage of fluidpast them and the washers or disks for helping compress the O-rings andfor helping to locate the piston, and further for acting as a wiper withits inner diameter on the outer diameter of the piston.

FIG. 3C illustrates a stack assembly 400 comprising, from left to right,washer 402, O-ring 410, washer 404, O-ring 412, washer 406, O-ring 414,washer 408, and O-ring 416. The O-rings on either end, here O-rings410/416, may sometimes be viewed as “primary” O-rings in that, in themanner of use as set forth more specifically below, O-ring 410 will sealagainst the passage of a pressurized fluid on its left from migratingacross the O-ring to the right (see FIGS. 3A and 3B), for example, afluid “A.” At the other end of the stack, O-ring 416 may seal againstthe passage of a fluid on its right, say fluid “B,” from migrating pastit and moving to the left as seen in FIG. 3C. That is to say, stackassembly 400 may be used, in one embodiment, to assist in the preventionof a migration of fluids across the O-rings on either end. For example,when one fluid on the left of the O-ring to the left of the stack and afluid on the right to the O-ring on the right end of the stack, theseprimary 410/416 or end placed O-rings will help prevent migration offluid either way, but will be primary to the fluids outside of them(fluid to the left on element 410, FIG. 3C, and to the right of O-ring416, FIG. 3C).

The primary, end placed O-rings 410/416 may be separated from, withwashers (404/406/408, FIG. 3C; 404/406/408, FIG. 3B), one or moreintermediate or backup O-rings (see 412 and 414, FIG. 3C; 412, FIGS. 3Aand 3B). These backup or intermediate O-rings may be between the endplaced O-rings and typically separated therefrom by washers. These arebackup in the sense that, if the primary O-rings perform properly, theywill maintain a fluid tight seal. However, should there be any leakagepast the primary O-rings, the backup O-rings should prevent leakageeither way, left or right, if there is leakage on either primary or endplaced O-ring.

FIGS. 3D and 3E illustrate an alternate preferred embodiment of stackassembly 400′, here comprising, between the primary O-rings 410/416, aslotted washer/unslotted washer pair 407/408, which slottedwasher/unslotted washer combination 407/408 includes one slotted washer407 with slots 407 a (see FIG. 3D). Slots 407 a are radially cut partlyinto one or both side walls between the inner diameter and the outerdiameter. The function of the slots is to help allow the passage (shouldeither primary O-ring leak) to assist in the passage of a fluid throughthe stack assembly for, preferably, flow out of vent 39 (see FIGS. 3A,3B, and 4). This vent helps prevent the fluids from mixing.

For example, FIGS. 3A and 3B both illustrate a valve having the slottedwasher/non-slotted washer 407/408 combination, that is, stack assembly400′. Turning to FIG. 3A, it may be seen that, if, for example, water onthe right side of O-ring 414 leaks through O-ring 414, it will, insqueezing past washer 408, work its way through slot or slots 407 a inwasher 407 and will find the easiest passage is out leak vent 39, ratherthan past either O-ring 410 or 412. Likewise, as seen in FIG. 3B,tetradecane 40 or other working fluid in fluid chamber 42 where thestack assembly is located may bypass O-ring 410, if O-ring 410 is faultyand backup O-ring 412 is faulty, but will then more easily work its wayout vent 39. This helps avoid contamination across pressure zonesseparating different fluids in the event that there may be O-ringfailure. In addition, the washers at their inner diameters tend to actas wipers on the outer surface of piston 38 as the piston, responsive tovolumetric changes in the fluid chamber of the fluid, moves to the leftand right between opened and closed positions.

Turning back to FIGS. 3A and 3B, one may see that working fluid islocated in a fluid chamber, which fluid chamber is substantially definedby the space to the left bore 419, the bore bearing part of piston 38,which has one end in the working fluid chamber, and the other end in thevalved fluid chamber (see also FIG. 11B). Moreover, it is seen thatwasher 402, the first washer to the left of O-ring 410, acts not only tohelp locate O-ring 410, but to seat the removed or right end of spring44. This may be compared to FIG. 3 or 4 above in which spring 44 simplyseats to the end of chamber 42. Indeed, FIGS. 3 and 4 compared to FIGS.3A and 3B indicate that the O-ring sets 33 a/33 b as seen in FIG. 3,which perform sealing functions to separate water and tetradecane, maybe removed and replaced as seen in FIGS. 3A and 3B with a single stack400 or 400′ (slotted), in which there are at least two end or primaryO-rings, here 410/414, which are spaced to either side of vent 39 and,in one embodiment, a vented set of washers, here slotted 407/unslotted408, adjacent vent 39, so as to help any leaked fluid bypassing eitherprimary O-ring into vent 39.

The use of Applicant's seal stock eliminates a machining step, that ofmachine the grooves for O-ring sets 33 a/33 b in FIG. 4. Indeed, thereare no O-ring grooves in FIGS. 3A and 3B, the O-rings acting as part ofa stack and located in the fluid chamber. “Effective” fluid chamber maybe deemed by length 442 (where the fluid meets the first O-ring), butthe machined fluid chamber, which carries the spring acting on thepiston end and the stack assembly 400/400′, which in turn acts on theremoved end of the machined fluid chamber 42, extends past vent 39, vent39 being isolated on the alkane side by at least primary O-ring 410 andback up 412, and on the water side by at least primary O-ring 414.

The inner diameter of a washer may be greater by about 4 mil (about 2mil per side) when compared to the OD of the piston. The outer diameterof the washer may be about 2 mil less than the inner diameter of theworking fluid chamber (about 1 mil per side). The O-ring inner diametercompared to the piston outer diameter may be greater by about 6 to 8 mil(about 3 to 4 mil per side).

The environment in which the stack assembly may be used is anyenvironment in which O-rings are used in conjunction with a piston toseparate different fluids under pressure. One such environment is thatof the freeze plug as used in the figures set forth elsewhere in thisapplication.

FIGS. 10A, B and C illustrate an integrated rod seal 400″ in which themultiplicity of ribs 420/422/424/426 are interspersed with amultiplicity of spacers 428/430/432, the ribs and spacers integral withone another and coupled to the piston (see FIG. 10C).

By integral or one-piece means that, unlike the previous embodiments,where there were separate O-rings and washers—instead there areelastomeric protrusions 420/422/424/426 which are connected by anintegral width-wise spacer elements 428/430/432. The protruding elementsmay be elastomeric and may be ribs and the entire structure may bemolded in one piece of elastomeric material, such as rubber orrubberlike material having, in one embodiment, a hardness of durometerof about 80 to 90. As seen in FIG. 10C, a protective washer 431 may beused between the sleeve-like integral stack 400′, which is entrainedupon the piston. As can be seen in FIG. 10C, there are still primary ribelements, one the rib all the way to the left (420) and all the way tothe right (426) and at least one secondary rib (two in FIG. 10A, one inFIG. 10C).

In one embodiment, the material is molded and about 80-90 durometer.Ribs extend both outward and inward like a stack of O-rings integratedor glued together. The multiple ribs of the one piece seal 400″ may wipethe rod multiple times with a minimum of drag. Drag is often a problemwith sealing. Wall clearance may be about 0.005 inches per side, insideand outside the groove on the spaces between the raised ribs.

Seal stack assembly 400/400′/400″ is useful as a seal in various valves,including those set forth in this application, and may consist of, inone embodiment, at least three elements:

1. At least one elastomeric element, such as an O-ring or other flexibleseal;

2. At least one hard washer of plastic or metal close fitting betweenthe bore of a chamber and the outer diameter of a piston rod;

3. A spring to compress the seal stack.

Multiple elastomeric elements may be stacked, alternately, with hardelements as necessary, each performing specific function, such as toprovide:

1. Sealing from leakage or contamination between a working fluid chamberand outside environment consisting of water at atmosphere;

2. Redundant sealing to provide backup for number 1 above;

3. Wiping of the rod to help ensure debris does not damage sealingO-rings.

Hard washers (such as nylon, Delrin® or Teflon®) may be inserted betweenelastomeric elements as required to provide:

1. Centering of piston OD (outer diameter) in chamber bore;

2. Distribute spring pressure compressing the stack; and

3. Provide two point support for piston rod to help keep it centered;

4. Additional scraping and wiping of rod by the hard washers will ensuredebris cannot damage sealing O-rings.

FIGS. 11A and 11B illustrate in an alternate preferred embodiment usefulfor temperature responsive valves, a machined body 500 that may includea working fluid chamber 502 for containing a piston 508 and spring 510.FIGS. 11A and 11B illustrate machined body 500 in which there is aworking fluid chamber 502, the working fluid chamber 502 containingpiston 508 and a spring 510 as in other embodiments illustrated herein.An end cap 512 and O-ring 514 may contain a working fluid, such astetradecane or other alcane, here designated fluid “A”, from a separatefluid “B,” which may be, in one embodiment, water. Piston 508 is seen tocomprise two sections 508 a/508 b, section 508 b having a smallerdiameter where it engages section 508 a. Captured O-ring 506 is capturedin a groove machined in body 500, unlike the O-rings of the stackassemblies set forth herein which ride in the chamber for the workingfluid. Moreover, it is seen in the valve opened position (FIG. 11A),O-ring 522 is a primary O-ring, as fluid will bypass O-ring 506, asO-ring 506 in the valve opened position is slightly spaced apart fromthe outer diameter of section 508 b of the piston. However, in a pistonclosed position (FIG. 11B), O-ring 506 is sealing against leakage offluid B from right to left as seen in FIG. 11B. In either valve openedor valve closed position, O-ring 520 of stack assembly 504 is theprimary O-ring to the left in the valve closed or valve opened positionswhile maintaining a seal to keep fluid A, in one embodiment,tetradecane, to the left of the O-ring.

A bore 519 is provided between working fluid chamber 502 having aworking fluid such as tetradecane and valved chamber 521 which maycontain a valved fluid such as Fluid “B.” The spring is entrained on afirst end of the piston, for example, the first end of the piston in theworking fluid chamber and up against the stack assembly 504. Stackassembly 504 may include a primary O-ring 520 and a secondary O-ring522, which may be flush against a bore end of the working fluid chamber.Washers 516 and 518 are provided first washer 516 for seating the springthereto. Spring 510 urges stack assembly 504 against the bore end wallof the working chamber as illustrated and temperature and phase changeof a working fluid such as tetradecane causes the piston to move to theright (warming, expanding, FIG. 11B) or to the left (cooling,contracting, FIG. 11A). In the operation of valve shown in FIGS. 11A and11B, it is seen that when the valve is closed bore mounted O-ring 506acts a primary for the movement of any fluid therepast (from right toleft as seen in FIG. 11B). On the other hand, when the valve is open asseen in FIG. 11A, and stack O-ring 522 is a primary, O-ring 520 is asecond primary and there is no secondary inbetween.

Any parts of the valve may be made of plastic or metal, in oneembodiment, the piston is metal, for example, stainless steel or copper,to enhance thermal conductivity. In another embodiment, the housingcomprising the body portions or any other parts disclosed herein may bemade of tough, durable plastic, such as an acetal plastic (such asDelrin®).

Although the invention has been described with reference to specificembodiments, this description is not meant to be construed in a limitingsense. On the contrary, various modifications of the disclosedembodiments will become apparent to those skilled in the art uponreference to the description of the invention. The number or order ofO-rings or washers may be varied as necessary or combined with theintegrated seal for specific requirements. It is therefore contemplatedthat the appended claims will cover such modifications, alternatives,and equivalents that fall within the true spirit and scope of theinvention.

1. In a valve having a body with a sealed working fluid chamber, a boreand a valved fluid chamber, the valved fluid chamber having an inlet andoutlet and a seat between the inlet and the outlet, a piston, the pistonfor extending through the bore from the working fluid chamber to thevalved fluid chamber, a spring for biasing the piston away from the seatand a working fluid for receipt in the working fluid chamber improvementcomprising: a seal stack assembly for entrainment, under compression,upon the piston and in the working fluid chamber between a working fluidchamber end wall and a first end of the piston, wherein the first end ofthe piston is located in the working fluid chamber and a second end inthe valved fluid chamber proximate the seat such that temperaturechanges cause the piston to move responsive to expansion and contractionof the working fluid between a seated and an unseated position, theunseated position for the passage of a fluid past the seat.
 2. The valveof claim 1, wherein the seal stack assembly comprises at least oneelastomeric element and adjacent thereto, one hard element, bothelements entrained upon the piston such that the spring urges the pistonaway from the seat.
 3. The valve of claim 2, wherein the hard element isa washer with at least one slot in a side wall thereof.
 4. The valve ofclaim 1, wherein the seal stack assembly comprises at least a firstwasher for receipt of the spring thereagainst, a first “O” ring forlaying flush against the first washer, a second washer, sandwichedbetween a second “O” ring and the first “O” ring.
 5. The valve of claim4, wherein at least one of the washers is slotted.
 6. The valve of claim5, wherein the working fluid chamber includes a vent located proximatethe seal stack assembly.
 7. The valve of claim 4, further including athird washer adjacent the second “O” ring.
 8. The valve of claim 7,wherein the third washer is slotted.
 9. The valve of claim 8, furtherincluding a vent proximate the slotted washer.
 10. The valve of claim 9,further including a fourth washer adjacent the third washer.
 11. Thevalve of claim 2, wherein the seal stack assembly is integrated and theelastomeric element is a first rib and the adjacent hard element is aspacer, and further including a second elastomeric element comprising asecond rib spaced apart from the first rib by the spacer.
 12. The valveof claim 1, further including an “O” ring located in the bore.
 13. Athermally actuated valve comprising: a housing having walls defining aninlet adapted to receive water under pressure, an outlet, a firstchamber fluidly connecting the inlet to the outlet, a second chamberhaving a near end and a removed end, walls defining a bore separatingthe first chamber from the second, longitudinal chamber; a resilientseat defining a seat plane, the seat for engaging the housing, the seatadjacent the inlet of the first chamber of the housing; a piston havinga first end that includes a nose and a second end and a longitudinalaxis, the piston partially disposed in the first chamber, partially andslidably disposed in the bore, and partially disposed in the secondchamber, the piston's longitudinal axis aligned substantiallyperpendicular to the seat plane; a spring for engaging the piston, so asto bias the piston towards the removed end of the second chamber; a sealstack assembly for fluid sealing between the piston and walls of thesecond longitudinal chamber and sandwiched under compression between thespring and walls of the second chamber to prevent fluid transfer betweenthe first chamber and the second chamber; and a working material sealedin the second chamber capable of moving the piston responsive totemperature changes between a seated position and an unseated position.14. The valve of claim 13, wherein the seal stack assembly comprises: awasher for receipt onto the piston and for receiving one end of thespring against a first surface thereof; a first “O” ring; a secondwasher; and a second “O” ring, the “O” rings and washers located betweenthe one end of the spring and the walls of the second chamber, andsandwiched under compression by the spring.
 15. The valve of claim 14,wherein at least one of the washers is slotted and further including avent in the second chamber proximate the slotted washer.
 16. The valveof claim 13, wherein the seal stack assembly is integral and comprisestwo elastomeric ribs adjacent a hard spacer.
 17. The valve of claim 13,wherein the outlet of the first chamber includes a vacuum break.
 18. Thevalve of claim 13, wherein the outlet of the first chamber includes adrain tube with a remote opening.
 19. The valve of claim 13, the sealstack assembly further including an “O” ring in the bore.
 20. Athermally actuated valve comprising: a housing having walls defining aninlet adapted to receive water under pressure, an outlet, a firstchamber fluidly connecting the inlet to the outlet, a second chamberhaving a near end and a removed end, walls defining a bore separatingthe first chamber from the second, longitudinal chamber; a resilientseat defining a seat plane, the seat for engaging the housing, the seatadjacent the inlet of the first chamber of the housing; a piston havinga first end that includes a nose and a second end and a longitudinalaxis, the piston partially disposed in the first chamber, partially andslidably disposed in the bore, and partially disposed in the secondchamber, the piston's longitudinal axis aligned substantiallyperpendicular to the seat plane; a spring for engaging the piston, so asto bias the piston towards the removed end of the second chamber; a sealstack assembly for fluid sealing between the piston and walls of thesecond longitudinal chamber and sandwiched under compression between thespring and walls of the second chamber to prevent fluid transfer betweenthe first chamber and the second chamber; and a working material sealedin the second chamber capable of moving the piston responsive totemperature changes between a seated position and an unseated position;wherein the seal stack assembly comprises: a washer for receipt onto thepiston and for receiving one end of the spring against a first surfacethereof; a first “O” ring; a second washer; and a second “O” ring; the“O” rings and washers located between the one end of the spring and thewalls of the second chamber, and sandwiched under compression by thespring; and wherein at least one of the washers is slotted and furtherincluding a vent in the second chamber proximate the slotted washer.